There are many pneumatically actuated valves for controlling gas flows in use for many applications. One example application is the use of pneumatic valves for controlling the flows of various gases into and out of vacuum chambers, including load lock vacuum chambers providing a buffer space for assisting the transfer of wafers into and out of vacuum coating or processing chambers, where such wafers, parts, or other substrates (hereinafter all called “wafers” for convenience) are coated with thin films of semiconductor and/or dielectric materials, or etched to removed a deposited material on the wafer surface. In such installations, the vacuum coating or processing chamber is generally maintained at a set vacuum range that is appropriate for the particular vacuum coating process that is being used, for example, a chemical vapor deposition (CVD) process, and a load lock chamber is connected to a slit wafer transfer valve or gate entrance of the vacuum chamber. The load lock chamber also has a slit gate opening to atmosphere. Wafers intended to be processed can be inserted from ambient atmospheric pressure into the load lock chamber, whereupon the slit gate opening to the ambient atmospheric pressure environment is closed, and the load lock chamber is then pumped down to the operating pressure range (vacuum) of the vacuum processing chamber. When the load lock chamber pressure with the wafers to be processed is evacuated to the operating pressure range of the vacuum processing chamber, the slit wafer transfer gate or valve separating the load lock chamber from the vacuum processing chamber is opened, and the wafers to be processed can then be transferred into the vacuum processing chamber for processing, e.g., for coating with a semiconductor film or other material. When the processing of the wafers in the vacuum processing chamber is completed, the finished (e.g., coated) wafers can be shuttled back into the load lock chamber. The slit wafer transfer gate or valve between the load lock chamber and the vacuum processing chamber can then be closed to isolate the vacuum processing chamber from the load lock chamber, and then air or other gas can be introduced into the load lock chamber to increase the pressure in the load lock chamber back up to ambient or atmospheric pressure so that the ambient slit can be opened and the finished, processed wafers can be removed. In some more complex processes, the load lock chamber can be connected to several vacuum processing chambers and used to shuttle wafers from one processing chamber to another, for example, at the same or at different vacuum processing pressure ranges with different process gases for different deposition coatings or layers to be applied to the wafers, or to etch the deposited materials on the wafer surface.
Persons skilled in the art know that turbulence in the load lock chamber can disturb and stir up particles in the load lock chamber and that such particles can contaminate the wafers before, during, or after processing in the processing chamber. To minimize such turbulence after the wafers are initially transferred into the load lock chamber from ambient pressure, it is a common practice to begin the process of evacuating, i.e., pumping the pressure down in, the load lock chamber slowly until the air or gas density, thus pressure, in the load lock chamber is reduced to some intermediate density or pressure before increasing the rate of pump-down or evacuation to reach the operating pressure range of the vacuum processing chamber.